Consider Azure VM scale sets for Workspaces

[jemrobinson]

:white_check_mark: Checklist

• [x] I have searched open and closed issues for duplicates.
• [x] This is a request for a new feature in the Data Safe Haven or an upgrade to an existing feature.
• [x] The feature is still missing in the latest version.
• [x] I have read through the documentation.
• [x] This isn't an open-ended question (open a discussion if it is).

:strawberry: Suggested change

We could use Azure VM Scale Sets (https://learn.microsoft.com/en-us/azure/virtual-machine-scale-sets/flexible-virtual-machine-scale-sets-portal) to automatically scale the number of deployed workspaces based on demand.

:steam_locomotive: How could this be done?

As each VMSS is limited to a single SKU we would probably want one for CPU-enabled and one for GPU-enabled machines.

[JimMadge]

Do you know how these work? I'm thinking about configuring networking and NFS/samba.

Can we run configuration at deploy time? Can we have a pre-configured image which all VMs are deployed from?

Tempted to move this to a later milestone.

[jemrobinson]

Yes, I think it probably should be moved to a later milestone. Just wanted to make sure we were thinking about it and moving it deliberately.